This is a strange place for this thread and perhaps it should be moved. However, if we are sticking to aircraft that did not see combat in WW2, we should add the North American Twin Mustang which has a speed of 482 mph at 21000 ft. for a later version according to Wikipedia. I don't know a speed for 1945 but it must be close to the Hornet and the Do 335. The Lockheed P-38L Lightning was probably the fastest twin that saw combat.

Several things to note about the Do 335A tested speed of 477mph. This was with the
DB603E engine. This was an 87 octane engine with a single stage variable speed
supercharger. Equiped with the DB603LA engine the speed was 495mph, original
Dornier charts of alt versus speed are around. The DB603LA engine was in service
with the 4 x Ta 152C delivered to the Luftwaffe, so it existed. There are also
original Dornier charts out.

See here (from Rudiger Kosins "The German Fighter", Kosin was the Ar 234 designer)

There was also the DB603N which was capable of around 2800hp using C3 fuel.
This engine should have pushed the Do 335 over into the 500mph territory I'd say 515 or so.

This was going to be a potent aircraft able to mix it with the jets till mid 1946

The Do 335 had a bomb bay, so this was the kind of penetration speed achievable.

I expect bomb aiming would be by the TSA-2D toss bombing sight or via electronic
guidance: the Oboe like EG-ON-II which used a boosted a pair of Freya radar IFF (FuG 25a)
or the new FuG 226 Neuling IFF which could function as a blind bombing system from the
begining and was begining to replace the FuG 25a IFF.

In noting the speeds of aircraft consider that the Do 335 with a single stage
supercharger may be just as fast at low and medium altitudes as one with a
single stage supercharger. GM1's runs were made as well.

As far as the P-51H goes; The famous 487mph was an engineering estimate. Fastest it
flew was 475mph, this being with 100/150 octane and ADI (water injection).
The British fitted some Mustang III with Merlin 100 engines which had two stage
three speed superchargers the same as the P-51H and they achieved about 465-469 mph
essentially the improved aerodynmaics of the P-51H was worth about 10 mph.

Would a P-51H catch a Do 335? In general, no, though it could be possible with height advantage
or in the case of being caught unawares essentially the the Do 335 was equally fast and in
the planed for Do 335 (DB603L) and DB603N versions significantly faster.

Would a P-51H catch a Do 335? In general, no, though it could be possible with height advantage
or in the case of being caught unawares essentially the the Do 335 was equally fast and in
the planed for Do 335 (DB603L) and DB603N versions significantly faster.

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An obsolete dinosaur by the time it was flying. As heavy as a B-25, its performance had already been eclipsed a year before by the 4000 lb lighter XP-72, cancelled because the Allies had the war won and was moving on to jets.

Would a P-51H catch a Do 335? In general, no, though it could be possible with height advantage
or in the case of being caught unawares essentially the the Do 335 was equally fast and in
the planed for Do 335 (DB603L) and DB603N versions significantly faster.

An obsolete dinosaur by the time it was flying. As heavy as a B-25, its performance had already been eclipsed a year before by the 4000 lb lighter XP-72, cancelled because the Allies had the war won and was moving on to jets.

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So what was the fastest speed a XP-72 flew in actual flight: straight and level. I believe it never hit more than 480mph. The elaborate turbo-compound system was never developed. What bomb bay size did the XP-72 have?

XP-72 and P-51H are mainly 'brochure talk' though obviously fast. The 550mph claimed speed is unbelievable.

Jumo 222E/F a massive 2900 hp engine with a two stage supercharger was also slated for the Do 335, that engine was actually ready and ordered into production after protracted development.

Hello Siegfried
the highest flown speed for Do 335 in the graph you posted is 750km/h (466mph), so if we are comparing flown speed that was the speed of Do 335 up to Dec 44, Hornet proto first flew Jul 44 and achieved 485mph (780km/h) in the end, cannot remember when.

Hello Siegfried
the highest flown speed for Do 335 in the graph you posted is 750km/h (466mph), so if we are comparing flown speed that was the speed of Do 335 up to Dec 44, Hornet proto first flew Jul 44 and achieved 485mph (780km/h) in the end, cannot remember when.

Juha

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The (beautiful) Hornet was around 460mph in operational form. Additionaly had zero limits for added horspower as the Merlins 130 were at the limit of their development and specially designed for the aircraft. Do 335 had greater potential not only from engines point of view but from its shape as well.And the internal bomb bay is huge advantage. I like very very much both of these planes.
However my latest passion in WW2 aircrafts is KI83. It appears that in american tests approached 462mph. It was equally beautiful with the Hornet. It was much much simpler than Do 335 , of conventional structure unlike Hornet,yet it managed similar performance. And it did it on radial engines! Built in Germany and equiped with Jumo 222 E/F it would be a monster ! Even with Db 603EM or Jumo 213E-1 would be top in speed.Yet it had ,in standart version room ,for second crewman without additional drug. So NF and bad weather mission convertions very easy. And of excellent agility like most japan aircrafts. In short excellent performance by a relatively simple aircraft.

Hello Jim
I agree with most. yes production Hornet was slower than the proto, but are we sure that fully combat ready Do 335 would have been as fast as the plane which achieved the highest speed in the test phase. IMHO probably not. And what was DB 603 A5? I must admit that I don't recall coming across it earlier. Even DB 603E engined plane was a bit slower, achieving something like 742-45km/h max speed. On development potential, now jet age was dawning, dH had Vampire on pipeline and one must remember that the captured 335s were problem children, plane was clearly not ready and full of system problems from landing gear onwards, so not near to effective combat use.
I also like Ki-83, also Hornet but I think that 335 was only very interesting construction, Ta 152C was more to my taste for a country which had limited fuel supplies. I tended to saw 335 as potentially effective night fighter.

Too bad for Germans they didn't produce it much earlier (but in a smaller shape, tailored for DB-601/605 and/or Jumo 211 - Davebender was posting something along these lines before), when another engine in a single-hull layout was still offering some benefits. Like for BoB or for jobs in MTO in Russia (possible pros: speed, armament - even if that's 8 LMGs initially, range probably).
A bomber destroyer of better performance armament than both Fw-190 and Me-410 for 1943-44?

Hello Siegfried
the highest flown speed for Do 335 in the graph you posted is 750km/h (466mph), so if we are comparing flown speed that was the speed of Do 335 up to Dec 44, Hornet proto first flew Jul 44 and achieved 485mph (780km/h) in the end, cannot remember when.

Juha

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The speed of 474 mph is assciated with the production Do 335A-1 (using MW50 boosted DB603E-1 engines) not shown in this early chart for A-0 aircraft. The speed was 474 mph at 21,325 ft with MW 50 boost. The do 335 consistantly exceded expectations.

As I pointed out, put in the Ta 152C DB603LA engine and speed is likely to be 495mph, perhaps more since boost levels went up after this chart was made.

Do 335B number 9-8604-B-1 did receive the DB605LA engine.

The Hornet prototype RR 915 first flew on 28 July 1944 with Geoffrey de Havilland Jr. at the controls. Powered by twin Merlin engines, it was the fastest piston-engined fighter in Royal Air Force service. The Hornet also has the distinction of being the fastest wooden aircraft ever built and the second fastest operational twin propeller-driven aircraft — being slightly slower than the unconventional German Dornier Do 335 of 1945.
The prototype achieved 485 mph (780 km/h) in level flight, which came down to 472 mph (760 km/h) in production aircraft.

The first 10 Do 335 A-0s were delivered for testing in May. By late 1944, the Do 335 A-1 was on the production line. This was similar to the A-0 but with the uprated DB 603 E-1 engines and two underwing hardpoints for additional bombs, drop tanks or guns. It was capable of a maximum speed of 763 km/h (474 mph) at 6,500 m (21,300 ft) with MW 50 boost, or 686 km/h (426 mph) without boost, and able to climb to 8,000 m (26,250 ft) in under 15 minutes. Even with one engine out, it could reach about 563 km/h (350 mph).

Thanks Siegfried
But 335 definitely didn't "consistantly exceded expectations." E-Kdo 335 report clearly stated that their Do 335s were slower than what had been claimed by Dornier and predicted that fully service equipped production planes might well be up to 20km/h slower still.

Thanks Siegfried
But 335 definitely didn't "consistantly exceded expectations." E-Kdo 335 report clearly stated that their Do 335s were slower than what had been claimed by Dornier and predicted that fully service equipped production planes might well be up to 20km/h slower still.
Juha

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Source? The use of two additional wing guns would've cost speed, but this is hardly neccessary given the high fire power of the 2 x MG 151 and 1 x MK 103 (30mm) gun.

What do you guys think about a potential Fw 187 with Jumo 213E/J/S? I guess it would be in the same class as the DH Hornet. In its original Form it had as slim a fuselage and engine nacelles as the Hornet.